The inspiratory to end-tidal oxygen difference during exercise.
OBJECTIVE
Fast paramagnetic oxygen analyzers have made it possible to measure inspiratory to end-tidal oxygen concentration difference (P(I-ET)O2) breath-by-breath. It is now frequently displayed on monitors during routine anesthesia. We wanted to study the effects of major changes in metabolism, ventilation and circulation on P(I-ET)O2.


METHODS
Ten healthy male volunteers were studied under exercise. P(I-ET)O2 was measured with a fast-response paramagnetic differential oxygen sensor. Cardiac output was measured with non-invasive transthoracic electrical bioimpedance. Metabolism was measured with indirect calorimetry and ventilation with a side stream spirometer. After a rest period, the subjects cycled at 30 W and 60 W, 6 minutes on each work load and were then observed during 10 minutes of rest.


RESULTS
P(I-ET)O2 corresponded well to VO2/VA (the oxygen uptake to alveolar ventilation quotient) correlation showed r = 0.79. P(I-ET)O2 was influenced by changes in cardiac output which occurred primarily at the start and at the end of exercise. Expired minute ventilation (VE) multiplied by P(I-ET)O2 was related to cardiac output with a high intrapersonal correlation.


CONCLUSIONS
P(I-ET)O2 is a good measure of adequate ventilation in relation to the oxygen consumption level and multiplied by VE it might offer a non-invasive bedside parameter indicating changes in cardiac output.
Bengtsson
J
J
Dep. of Pediatric Anesthesia and Intensive Care, Ostra Hospital, Göteborg University, Sweden.
Bengtson
J P
JP
D000328:Adult; D002302:Cardiac Output; D004578:Electron Spin Resonance Spectroscopy; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D010100:Oxygen / Q000032:analysis*; D010101:Oxygen Consumption; D019095:Point-of-Care Systems; D012123:Pulmonary Ventilation; D013990:Tidal Volume
D010100:Oxygen